Process of preparing substituted



' scribed hereinafter. substituted melamines are prepared may be illus-PatenteclJan. 8, I946 Daniel E. Nagy, Stamford, Conn., assignor toAmerican Cyanamid Company, New York, N. Y., a corporation of Maine- NoDrawing. Application September 14, 1944, Serial No. 554,154

8 Claims.

This invention relates to a. new method of preparing substitutedmelamines.

I have discovered that aliphatic-, cycloaliphatic-, andaromatic-substituted melamines can be prepared by causing aliphatic,cycloaliphatic and aromatic secondary amines to react with1,3-dicyanoguanid1'ne under the conditions de- The reaction whereby thetrated by means of the following equation.- As a r first step in thereaction, a salt is probably formed by the secondary amine and theacidic cyanoguanidine as follows:

n heating, the. 1,3-dicyanoguanidine amine salt .of one of its alkalimetal salts, I prefer to use the alkalimetal salts of1,3-dicyanoguanidine in my new reaction in the preparation orNidisubstituted melamines.

The preferred reactants of the present invention comprise a salt of asecondary amine and an alkali metal salt of 1,3-dicyanoguanidine. Theuse of these salts does not efiect the ultimate outcome of the reactioninasmuch as during the first stages of the reaction the acidic portionof the secondary amine salt reacts with the alkali metal salt of the1.3-.dicyanoguanidine resulting in the formation of an inorganic salt,

' such as potassium chloride, and the amine salt of 1,3-dicyanoguanidineas illustrated in the first equation above. I may, of course, use thetree amine base and the free 1,3-dicyanoguahidine acid as illustrated,but for reasons just stated rearranges and a Ni-di-substituted' melamineis formed as rollows:

the respective salts of these ferred.

A large number and variety of secondary amines may be used in accordancewith my process to prepare the corresponding substituted melamines.ondary amines as diethylamine, dimethylamine, di-n-butylamine,di-isopropylamine, didodecylamine, dioctadecylamine, morpholine,piperidine, dicyclohexylamine, methylaniline, methylnitroaniline,ethylaniline, diphenylamine, '2,3-benzopiperidine, etc. These secondaryamine are used in the form of their free bases or in the form of one oftheir acid salts such as the hydrochloride, phosphate, nitrate,carbonate, or the like.

The 1,3-dicyanoguanidine may he used in the form of the free acid or asone of its many salts such as for example, potassium, sodium, ammonium,'guanidine, magnesium, calcium, stronmaterials are pretium or the like.

by mixin together dicyandiamide, a water soluble alkali metal oralkaline earth metal hydroxide and thereafter adding cyanogen chloride.I

Ordinarily the product is obtained in the form of an alkali metal oralkaline earth metal salt, but the free acid may be obtained byneutralizing.

the alkali metal or alkaline earth metal saltforming group with a stronginorganic acid,

Various other metal, ammonium and amine salts of 1,3-'di-cyanoguanidinemay be prepared by neutralization of the free acid or by methods ofdouble decomposition.- Since the l,3-dic yanoguanidine is most easilyobtained in the form used if desired. The temperature of the reaction isnot particularly critical. Any temperature from about 60 C, or higher,up to the decomposition point of the product, may be used. Thetemperature of a steam bath, about 0.,

is suitable, but temperatures up to 200 C. may be used to advantage whenheating the materials together in the absence of a solvent.

Although it is not necessary to regulate the pH of the reaction mixture,it is found that the I may, for example, use such secaliphatic aminesreact best at a pH between six and eight, whereas the aromatic aminesappear to react best at a pH ofabout two to seven. Both the aliphaticand aromatic amines will react with 1,3-dicyanoguanidine under other pHconditions, however.

My invention will now be illustrated in greater particularityby means ofthe following specific examples: It will be understood, of course, thatthese examples are merely illustrative and are not intended to limit myinvention to the particular reactants or conditions described there n. aAll parts are by weight unless otherwise indicated.

Example 1 11.0 g. (0.1 mol) ofdiethylamine hydrochloride and'14.'7 g.(0.1 mol) ofmono-potassium 1,3-dicyanoguanidinewere heated in an oilbath kept at 150 C. At 60 C. the mixture became soft;

at 98 C., pasty; andat 145 C. an exothermic reaction caused thetemperature to rise to 190 C. After cooling in an ice bath the material,

which was now a thick gum, ,was heated at 145 C. for 45 minutes or untilheat was no longer evolved. The product was dissolved in dilutehydrochloric acid, filtered, and reprecipitated to.

obtain '7 g. of slightly impure Ni-diethyl melamine. The product wasdissolved, in methanol, the insoluble impurities separated by filtrationand the diethyl melamine was precipitated by dilution of the filtratewith-water,

Example 2 165 g. (1.0 mol) of N-dibutylamine hydrochloride and 147 g.(1.0 mol) of mono-potassium 1,3- dicyanoguanidine were mixed togetherasthoroughly as possible in a mortar. The mixture was spr ad on trays andheated in a forced-draft oven at 38 C. for about 4 hours. The dibutylmelamine which formed was extracted from the solid by means of about 400cc. of hot methanol and then precipitated by the addition of water andalkali. then transformed to the hot-water soluble nitrate ,salt bytreatment with nitric acid. The Ni-dibutyl melamine recovered from thenitrate salt.

upon neutralization with alkali was further purified' by dissolving inacetone, filtering and then crystallizing by the addition of an equalamount of water. The crystalline solid melted to a clear liquid at134-135'C'. The melting point of the solid when mixedwith a known sample01. Ni-dibutyl melamine was the same.

' Example 3' To an aqueous suspension of 42.8 g. (0.4 mol) ofmethylaniline in 100 cc. of water was added 50 cc. of dilutedhydrochloric acid (70 cc. concentrated hydrochloric acid diluted to 200cc. with water). The pH of the resulting solution was aseasos aboutthree. Four-tenths of a mo! ot potassium dicyanoguanidine (62 g'.) wasadded over a period of about 10 minutes to the solution, and the-mixture was then heated to 95- C. Durlng the course of the reaction, about45 minutes, 130 co. more 01 the diluted hydrochloric acid was added fromtime to time to keepthe pH within the range of about two to three, Oncooling the solution there was obtained 101 g. or Nr-methyl-Ni-phenylmelamine hydrochloride. After filtering oi! the crystals 9.7 g. ofNr-methyl-Ni-phenyl melamine was 2. A method of preparingNr-di-substituted melamines which comprises mixing together-a secondaryamine saltvof an acid and a salt of 1,-3-dicyanoguanidine and heatingthe mixture.

' 3., A method of preparing Ni-di-aliphatic-substituted melamines whichcomprises mixing together an aliphatic secondary amine salt of an acidand a salt of 1,3-dicyanoguanidine and heat ing the mixture.

The free dibutyl-melamine base was 4. A method of preparingNi-di-aromatic-substituted melamines which comprises mixing together anaromatic secondary amine salt of an acid and a salt of1,3-dicyanoguanidine and heating the mixture. I 1

5. A method of preparing Ni-di-substituted melamines which comprisesmixing together a secondary amine salt of a mineral acid and an alkalimetal saltof 1,3-dicyanoguanidine and heating the mixture at atemperature of at least ,60 C. until a substituted melamine is obtained.

6. A method of preparing Ni-di-aliphatic-sub stituted melamlnes whichcomprises mixing to. gether' an aliphatic secondar amine salt of amineral acid and potassium 1,3-dicyanoguanidine and heating thereactionmixture at a temperature of at least 60 C. until'a substitutedmelamine is formed.

7. A method of preparing dicyanoguanidine and heating the reactionmixture to at least 60? C. while maintaining the pH within the range ofabout two to seven until Ni-methyl-Nr-phenyl melamine is formed. j

8. A method of preparing Nr-diethyl melamine which comprises mixingtogether diethylamine hydrochloride and potassium 1,3-dicyanoguanidineandheating the reaction mixture to at least. 60 C.'until Nr-diethylmelamine is formed.

DANIEL E. NAGY.

Ni-methyl-Ni-phenylmelamine which comprises mixing togethermethylaniline hydrochloride and potassium 1.3-

